#include <linux/err.h>
#include <linux/fs.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/version.h>
#include <linux/stat.h>
#include <linux/namei.h>

#include "allowlist.h"
#include "klog.h" // IWYU pragma: keep
#include "manager.h"
#include "throne_tracker.h"
#include "apk_sign.h"
#include "dynamic_manager.h"
#include "throne_comm.h"

uid_t ksu_manager_uid = KSU_INVALID_UID;
static uid_t locked_manager_uid = KSU_INVALID_UID;
static uid_t locked_dynamic_manager_uid = KSU_INVALID_UID;

#define KSU_UID_LIST_PATH "/data/misc/user_uid/uid_list"
#define SYSTEM_PACKAGES_LIST_PATH "/data/system/packages.list"

struct uid_data {
    struct list_head list;
    u32 uid;
    char package[KSU_MAX_PACKAGE_NAME];
};

// Try read /data/misc/user_uid/uid_list
static int uid_from_um_list(struct list_head *uid_list)
{
    struct file *fp;
    char *buf = NULL;
    loff_t size, pos = 0;
    ssize_t nr;
    int cnt = 0;

    fp = filp_open(KSU_UID_LIST_PATH, O_RDONLY, 0);
    if (IS_ERR(fp))
        return -ENOENT;

    size = fp->f_inode->i_size;
    if (size <= 0) {
        filp_close(fp, NULL);
        return -ENODATA;
    }

    buf = kzalloc(size + 1, GFP_ATOMIC);
    if (!buf) {
        pr_err("uid_list: OOM %lld B\n", size);
        filp_close(fp, NULL);
        return -ENOMEM;
    }

    nr = kernel_read(fp, buf, size, &pos);
    filp_close(fp, NULL);
    if (nr != size) {
        pr_err("uid_list: short read %zd/%lld\n", nr, size);
        kfree(buf);
        return -EIO;
    }
    buf[size] = '\0';

    for (char *line = buf, *next; line; line = next) {
        next = strchr(line, '\n');
        if (next) *next++ = '\0';

        while (*line == ' ' || *line == '\t' || *line == '\r') ++line;
        if (!*line) continue;

        char *uid_str = strsep(&line, " \t");
        char *pkg     = line;
        if (!pkg) continue;
        while (*pkg == ' ' || *pkg == '\t') ++pkg;
        if (!*pkg)   continue;

        u32 uid;
        if (kstrtou32(uid_str, 10, &uid)) {
            pr_warn_once("uid_list: bad uid <%s>\n", uid_str);
            continue;
        }

        struct uid_data *d = kzalloc(sizeof(*d), GFP_ATOMIC);
        if (unlikely(!d)) {
            pr_err("uid_list: OOM uid=%u\n", uid);
            continue;
        }

        d->uid = uid;
        strscpy(d->package, pkg, KSU_MAX_PACKAGE_NAME);
        list_add_tail(&d->list, uid_list);
        ++cnt;
    }

    kfree(buf);
    pr_info("uid_list: loaded %d entries\n", cnt);
    return cnt > 0 ? 0 : -ENODATA;
}

static int get_pkg_from_apk_path(char *pkg, const char *path)
{
    int len = strlen(path);
    if (len >= KSU_MAX_PACKAGE_NAME || len < 1)
        return -1;

    const char *last_slash = NULL;
    const char *second_last_slash = NULL;

    int i;
    for (i = len - 1; i >= 0; i--) {
        if (path[i] == '/') {
            if (!last_slash) {
                last_slash = &path[i];
            } else {
                second_last_slash = &path[i];
                break;
            }
        }
    }

    if (!last_slash || !second_last_slash)
        return -1;

    const char *last_hyphen = strchr(second_last_slash, '-');
    if (!last_hyphen || last_hyphen > last_slash)
        return -1;

    int pkg_len = last_hyphen - second_last_slash - 1;
    if (pkg_len >= KSU_MAX_PACKAGE_NAME || pkg_len <= 0)
        return -1;

    // Copying the package name
    strncpy(pkg, second_last_slash + 1, pkg_len);
    pkg[pkg_len] = '\0';

    return 0;
}

static void crown_manager(const char *apk, struct list_head *uid_data, int signature_index)
{
    char pkg[KSU_MAX_PACKAGE_NAME];
    if (get_pkg_from_apk_path(pkg, apk) < 0) {
        pr_err("Failed to get package name from apk path: %s\n", apk);
        return;
    }

    pr_info("manager pkg: %s, signature_index: %d\n", pkg, signature_index);

#ifdef KSU_MANAGER_PACKAGE
    // pkg is `/<real package>`
    if (strncmp(pkg, KSU_MANAGER_PACKAGE, sizeof(KSU_MANAGER_PACKAGE))) {
        pr_info("manager package is inconsistent with kernel build: %s\n",
                KSU_MANAGER_PACKAGE);
        return;
    }
#endif
    struct uid_data *np;

    list_for_each_entry(np, uid_data, list) {
        if (strncmp(np->package, pkg, KSU_MAX_PACKAGE_NAME) == 0) {
            bool is_dynamic = (signature_index == DYNAMIC_SIGN_INDEX || signature_index >= 2);

            if (is_dynamic) {
                if (locked_dynamic_manager_uid != KSU_INVALID_UID && locked_dynamic_manager_uid != np->uid) {
                    pr_info("Unlocking previous dynamic manager UID: %d\n", locked_dynamic_manager_uid);
                    ksu_remove_manager(locked_dynamic_manager_uid);
                    locked_dynamic_manager_uid = KSU_INVALID_UID;
                }
            } else {
                if (locked_manager_uid != KSU_INVALID_UID && locked_manager_uid != np->uid) {
                    pr_info("Unlocking previous manager UID: %d\n", locked_manager_uid);
                    ksu_invalidate_manager_uid(); // unlock old one
                    locked_manager_uid = KSU_INVALID_UID;
                }
            }

            pr_info("Crowning %s manager: %s (uid=%d, signature_index=%d)\n",
                    is_dynamic ? "dynamic" : "traditional", pkg, np->uid, signature_index);

            if (is_dynamic) {
                ksu_add_manager(np->uid, signature_index);
                locked_dynamic_manager_uid = np->uid;

                // If there is no traditional manager, set it to the current UID
                if (!ksu_is_manager_uid_valid()) {
                    ksu_set_manager_uid(np->uid);
                    locked_manager_uid = np->uid;
                }
            } else {
                ksu_set_manager_uid(np->uid); // throne new UID
                locked_manager_uid = np->uid; // store locked UID
            }
            break;
        }
    }
}

#define DATA_PATH_LEN 384 // 384 is enough for /data/app/<package>/base.apk

struct data_path {
    char dirpath[DATA_PATH_LEN];
    int depth;
    struct list_head list;
};

struct apk_path_hash {
    unsigned int hash;
    bool exists;
    struct list_head list;
};

static struct list_head apk_path_hash_list = LIST_HEAD_INIT(apk_path_hash_list);

struct my_dir_context {
    struct dir_context ctx;
    struct list_head *data_path_list;
    char *parent_dir;
    void *private_data;
    int depth;
    int *stop;
};
// https://docs.kernel.org/filesystems/porting.html
// filldir_t (readdir callbacks) calling conventions have changed. Instead of returning 0 or -E... it returns bool now. false means "no more" (as -E... used to) and true - "keep going" (as 0 in old calling conventions). Rationale: callers never looked at specific -E... values anyway. -> iterate_shared() instances require no changes at all, all filldir_t ones in the tree converted.
#if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 1, 0)
#define FILLDIR_RETURN_TYPE bool
#define FILLDIR_ACTOR_CONTINUE true
#define FILLDIR_ACTOR_STOP false
#else
#define FILLDIR_RETURN_TYPE int
#define FILLDIR_ACTOR_CONTINUE 0
#define FILLDIR_ACTOR_STOP -EINVAL
#endif
FILLDIR_RETURN_TYPE my_actor(struct dir_context *ctx, const char *name,
                             int namelen, loff_t off, u64 ino,
                             unsigned int d_type)
{
    struct my_dir_context *my_ctx =
        container_of(ctx, struct my_dir_context, ctx);
    char dirpath[DATA_PATH_LEN];

    if (!my_ctx) {
        pr_err("Invalid context\n");
        return FILLDIR_ACTOR_STOP;
    }
    if (my_ctx->stop && *my_ctx->stop) {
        pr_info("Stop searching\n");
        return FILLDIR_ACTOR_STOP;
    }

    if (!strncmp(name, "..", namelen) || !strncmp(name, ".", namelen))
        return FILLDIR_ACTOR_CONTINUE; // Skip "." and ".."

    if (d_type == DT_DIR && namelen >= 8 && !strncmp(name, "vmdl", 4) &&
         !strncmp(name + namelen - 4, ".tmp", 4)) {
         pr_info("Skipping directory: %.*s\n", namelen, name);
         return FILLDIR_ACTOR_CONTINUE; // Skip staging package
     }
    
    if (snprintf(dirpath, DATA_PATH_LEN, "%s/%.*s", my_ctx->parent_dir,
             namelen, name) >= DATA_PATH_LEN) {
        pr_err("Path too long: %s/%.*s\n", my_ctx->parent_dir, namelen,
               name);
        return FILLDIR_ACTOR_CONTINUE;
    }

    if (d_type == DT_DIR && my_ctx->depth > 0 &&
        (my_ctx->stop && !*my_ctx->stop)) {
        struct data_path *data = kmalloc(sizeof(struct data_path), GFP_ATOMIC);

        if (!data) {
            pr_err("Failed to allocate memory for %s\n", dirpath);
            return FILLDIR_ACTOR_CONTINUE;
        }

        strscpy(data->dirpath, dirpath, DATA_PATH_LEN);
        data->depth = my_ctx->depth - 1;
        list_add_tail(&data->list, my_ctx->data_path_list);
    } else {
        if ((namelen == 8) && (strncmp(name, "base.apk", namelen) == 0)) {
            struct apk_path_hash *pos, *n;
#if LINUX_VERSION_CODE < KERNEL_VERSION(4, 8, 0)
            unsigned int hash = full_name_hash(dirpath, strlen(dirpath));
#else
            unsigned int hash = full_name_hash(NULL, dirpath, strlen(dirpath));
#endif
            list_for_each_entry(pos, &apk_path_hash_list, list) {
                if (hash == pos->hash) {
                    pos->exists = true;
                    return FILLDIR_ACTOR_CONTINUE;
                }
            }

            int signature_index = -1;
            bool is_multi_manager = is_dynamic_manager_apk(
                dirpath, &signature_index);

            pr_info("Found new base.apk at path: %s, is_multi_manager: %d, signature_index: %d\n",
                dirpath, is_multi_manager, signature_index);
                
            // Check for dynamic sign or multi-manager signatures
            if (is_multi_manager && (signature_index == DYNAMIC_SIGN_INDEX || signature_index >= 2)) {
                crown_manager(dirpath, my_ctx->private_data, signature_index);
                
                struct apk_path_hash *apk_data = kmalloc(sizeof(struct apk_path_hash), GFP_ATOMIC);
                if (apk_data) {
                    apk_data->hash = hash;
                    apk_data->exists = true;
                    list_add_tail(&apk_data->list, &apk_path_hash_list);
                }
            } else if (is_manager_apk(dirpath)) {
                crown_manager(dirpath, my_ctx->private_data, 0);
                *my_ctx->stop = 1;

                // Manager found, clear APK cache list
                list_for_each_entry_safe (pos, n, &apk_path_hash_list, list) {
                    list_del(&pos->list);
                    kfree(pos);
                }
            } else {
                struct apk_path_hash *apk_data = kmalloc(sizeof(struct apk_path_hash), GFP_ATOMIC);
                if (apk_data) {
                    apk_data->hash = hash;
                    apk_data->exists = true;
                    list_add_tail(&apk_data->list, &apk_path_hash_list);
                }
            }
        }
    }

    return FILLDIR_ACTOR_CONTINUE;
}

void search_manager(const char *path, int depth, struct list_head *uid_data)
{
    int i, stop = 0;
    struct list_head data_path_list;
    INIT_LIST_HEAD(&data_path_list);
    unsigned long data_app_magic = 0;
    
    // Initialize APK cache list
    struct apk_path_hash *pos, *n;
    list_for_each_entry (pos, &apk_path_hash_list, list) {
        pos->exists = false;
    }

    // First depth
    struct data_path data;
    strscpy(data.dirpath, path, DATA_PATH_LEN);
    data.depth = depth;
    list_add_tail(&data.list, &data_path_list);

    for (i = depth; i >= 0; i--) {
        struct data_path *pos, *n;

        list_for_each_entry_safe (pos, n, &data_path_list, list) {
            struct my_dir_context ctx = { .ctx.actor = my_actor,
                                          .data_path_list = &data_path_list,
                                          .parent_dir = pos->dirpath,
                                          .private_data = uid_data,
                                          .depth = pos->depth,
                                          .stop = &stop };
            struct file *file;

            if (!stop) {
                file = filp_open(pos->dirpath, O_RDONLY | O_NOFOLLOW, 0);
                if (IS_ERR(file)) {
                    pr_err("Failed to open directory: %s, err: %ld\n",
                           pos->dirpath, PTR_ERR(file));
                    goto skip_iterate;
                }

                // grab magic on first folder, which is /data/app
                if (!data_app_magic) {
                    if (file->f_inode->i_sb->s_magic) {
                        data_app_magic = file->f_inode->i_sb->s_magic;
                        pr_info("%s: dir: %s got magic! 0x%lx\n", __func__,
                                pos->dirpath, data_app_magic);
                    } else {
                        filp_close(file, NULL);
                        goto skip_iterate;
                    }
                }

                if (file->f_inode->i_sb->s_magic != data_app_magic) {
                    pr_info("%s: skip: %s magic: 0x%lx expected: 0x%lx\n",
                            __func__, pos->dirpath,
                            file->f_inode->i_sb->s_magic, data_app_magic);
                    filp_close(file, NULL);
                    goto skip_iterate;
                }

                iterate_dir(file, &ctx.ctx);
                filp_close(file, NULL);
            }
        skip_iterate:
            list_del(&pos->list);
            if (pos != &data)
                kfree(pos);
        }
    }

    // Remove stale cached APK entries
    list_for_each_entry_safe (pos, n, &apk_path_hash_list, list) {
        if (!pos->exists) {
            list_del(&pos->list);
            kfree(pos);
        }
    }
}

static bool is_uid_exist(uid_t uid, char *package, void *data)
{
    struct list_head *list = (struct list_head *)data;
    struct uid_data *np;

    bool exist = false;
    list_for_each_entry (np, list, list) {
        if (np->uid == uid % 100000 &&
            strncmp(np->package, package, KSU_MAX_PACKAGE_NAME) == 0) {
            exist = true;
            break;
        }
    }
    return exist;
}

void track_throne(void)
{
    struct list_head uid_list;
    struct uid_data *np, *n;
    struct file *fp;
    char chr = 0;
    loff_t pos = 0;
    loff_t line_start = 0;
    char buf[KSU_MAX_PACKAGE_NAME];
    static bool manager_exist = false;
    static bool dynamic_manager_exist = false;
    int current_manager_uid = ksu_get_manager_uid() % 100000;

    // init uid list head
    INIT_LIST_HEAD(&uid_list);

    if (ksu_uid_scanner_enabled) {
        pr_info("Scanning %s directory..\n", KSU_UID_LIST_PATH);

        if (uid_from_um_list(&uid_list) == 0) {
            pr_info("Loaded UIDs from %s success\n", KSU_UID_LIST_PATH);
            goto uid_ready;
        }

        pr_warn("%s read failed, fallback to %s\n",
            KSU_UID_LIST_PATH, SYSTEM_PACKAGES_LIST_PATH);
    }

    {
        fp = filp_open(SYSTEM_PACKAGES_LIST_PATH, O_RDONLY, 0);
        if (IS_ERR(fp)) {
            pr_err("%s: open " SYSTEM_PACKAGES_LIST_PATH " failed: %ld\n", __func__, PTR_ERR(fp));
            return;
        }

        for (;;) {
            ssize_t count =
                kernel_read(fp, &chr, sizeof(chr), &pos);
            if (count != sizeof(chr))
                break;
            if (chr != '\n')
                continue;

            count = kernel_read(fp, buf, sizeof(buf),
                            &line_start);
            struct uid_data *data =
                kzalloc(sizeof(struct uid_data), GFP_ATOMIC);
            if (!data) {
                filp_close(fp, 0);
                goto out;
            }

            char *tmp = buf;
            const char *delim = " ";
            char *package = strsep(&tmp, delim);
            char *uid = strsep(&tmp, delim);
            if (!uid || !package) {
                pr_err("update_uid: package or uid is NULL!\n");
                break;
            }

            u32 res;
            if (kstrtou32(uid, 10, &res)) {
                pr_err("update_uid: uid parse err\n");
                break;
            }
            data->uid = res;
            strncpy(data->package, package, KSU_MAX_PACKAGE_NAME);
            list_add_tail(&data->list, &uid_list);
            // reset line start
            line_start = pos;
        }

        filp_close(fp, 0);
    }

uid_ready:
    // first, check if manager_uid exist!
    list_for_each_entry(np, &uid_list, list) {
        if (np->uid == current_manager_uid) {
            manager_exist = true;
            break;
        }
    }

    if (!manager_exist && locked_manager_uid != KSU_INVALID_UID) {
        pr_info("Manager APK removed, unlock previous UID: %d\n",
                locked_manager_uid);
        ksu_invalidate_manager_uid();
        locked_manager_uid = KSU_INVALID_UID;
    }

    // Check if the Dynamic Manager exists (only check locked UIDs)
    if (ksu_is_dynamic_manager_enabled() &&
        locked_dynamic_manager_uid != KSU_INVALID_UID) {
        list_for_each_entry(np, &uid_list, list) {
            if (np->uid == locked_dynamic_manager_uid) {
                dynamic_manager_exist = true;
                break;
            }
        }

        if (!dynamic_manager_exist) {
            pr_info("Dynamic manager APK removed, unlock previous UID: %d\n",
                    locked_dynamic_manager_uid);
            ksu_remove_manager(locked_dynamic_manager_uid);
            locked_dynamic_manager_uid = KSU_INVALID_UID;
        }
    }

    bool need_search = !manager_exist;
    if (ksu_is_dynamic_manager_enabled() && !dynamic_manager_exist)
        need_search = true;

    if (need_search) {
        pr_info("Searching for manager(s)...\n");
        search_manager("/data/app", 2, &uid_list);
        pr_info("Manager search finished\n");
    }
    
    // then prune the allowlist
    ksu_prune_allowlist(is_uid_exist, &uid_list);
out:
    // free uid_list
    list_for_each_entry_safe(np, n, &uid_list, list) {
        list_del(&np->list);
        kfree(np);
    }
}

void ksu_throne_tracker_init(void)
{
    // nothing to do
}

void ksu_throne_tracker_exit(void)
{
    // nothing to do
}